The same Scribunto oddity that broke Special:Version in T66069 also causes an unexpected result in siteinfo.showhooks (search for ParserLimitReport). In JSON, every other subscriber appears as a string in the subscribers array. For the anomalous Scribunto entry, the supposed array is instead output as an object. It gets even weirder in XML, where the "scribunto" and subscriber appear as an attribute of <subscribers> instead of as an element in their own right.

Note: I've also posted about this anomaly on the Scribunto talk page on MW.